<!-- This document is used to report back to its parent (1) a message indicating
     initial load, and (2) a message ACKing the result of moveBefore() being
     called in the parent. It helps the parent test that this subframe was not
     reloaded after moveBefore() is called on it -->
<!DOCTYPE html>
<body>
<script>
  window.onload = e => {

    window.onmessage = e => {
      if (e.data === 'after moveBefore') {
        window.parent.postMessage('ack after moveBefore', '*');
      }
    }

    window.parent.postMessage('loaded', '*');
  }
</script>
</body>
